The present invention relates to a clutch arrangement, in particular for a vehicle drive train, having a rotary element which is mounted on a housing so as to be rotatable about a longitudinal axis and which defines a cavity; a clutch which has a first clutch element and a second clutch element which can be coupled thereto, which clutch is arranged in the cavity, wherein the first clutch element or the second clutch element is coupled to the rotary element; and having a fluidic actuator arrangement which has a first and a second actuator element which can move relative to one another in order to activate the clutch.
Such clutch arrangements are used, for example, in vehicle drive trains as starter clutches which are arranged between an internal combustion engine and a speed-transforming gearbox. In addition such clutch arrangements are used as locking clutches. These may be, for example, what are referred to as “hang-on clutches” which, in order to set a four-wheel drive mode when necessary, connect a second driven axle to a cardan shaft or the like. However, such locking clutches can also be used as transverse locking clutches, wherein, for example, a right-hand and a left-hand drive shaft of a driven axle can be connected to one another in order in this way to set a transverse locking function. In addition, such locking clutches can be used in twin clutch arrangements which connect one output of a drive unit without a mechanical differential to a left-hand or right-hand drive shaft of a driven axle.
In such locking clutches, what are referred to as passive locking clutches are known in which a locking torque which cannot be influenced is set on the basis of a difference in rotational speed or difference in torque between the wheels or the axles. In this context, systems which sense the rotational speed include what are referred to as a visco clutch. In contrast, what are referred to as torsen differentials operate in a torque-sensing fashion.
In addition, what are referred to as active locks, which can be easily integrated into electronic drive control systems such as ABS (anti-skid) or ESP (traction control), are known. Active locks can be activated or deactivated at any time independently of differential rotational speeds, as a result of which interference torques associated with passive lock systems which could disrupt the electronic control systems are prevented. Friction clutches are generally used in the active locking clutches. Owing to the good meterability and the good wear behaviour, these friction clutches can be embodied as wet multi-plate clutches.
In the transverse locking clutches, rotational speed compensation can be limited owing to a mechanical differential of a driven axle. The advantage of such transverse locking clutches is that they can also be used in vehicles which are driven with just one axle, wherein properties can be obtained which are close to those of a sporty all-wheel drive. Such transverse locking clutches can, for example, be flange-connected to the outside of a gearbox housing as additional clutches and connected in a rotationally fixed fashion to a differential basket via a keyed joint toothing. However, it is also known to integrate such transverse locking clutches into the gearbox in order to save installation space, weight and assembly costs.
In order to activate such clutch arrangements it is known to provide, in a housing, a hydraulic pressure piston which, when pressure is applied, presses onto the clutch elements (for example multi-plate pack) via an arrangement composed of an axial bearing and a pressure plate. In these arrangements, the clutch arrangement does not form a system which is closed in itself, making handling complex in the case of integration and requiring changes to the gearbox housing. This in turn results in higher production costs.
In addition, concepts are known which are based on a rotating pressure piston. In this context, the hydraulic pressure is transferred from a housing, in which a pressure source is located, to the rotating locking clutch and the pressure piston integrated therein, via what is referred to as a rotary bushing. In this embodiment, no axial bearings are necessary. When such a co-rotating piston is used, the clutch arrangement can be embodied as an enclosed system which can be integrated into a gearbox using clearly defined existing interfaces. However, the required rotary bushing is technically very demanding and is generally associated with a relatively high leakage rate. This makes the use of a common pressure source difficult in the case of integration into an existing gearbox. In addition, the compensation of centrifugal forces which occur in the pressure piston is structurally complex and therefore expensive.
In order to activate such clutch arrangements it is also known to use ball ramp systems (“ETM”). In these ball ramp systems, an electric motor drives a ball ramp via a strong transmission ratio. As a result of the gradient in the raceway, an axial force is generated which compresses a multi-plate pack and as a result permits torque to be transmitted.
Although such ball ramp systems can be made very short in the axial direction, the relatively large electric motor has to be installed in the direct vicinity of the coupling system owing to the mechanical transmission of force.
In addition it is known to activate clutch arrangements via an electromagnetically actuated pilot control clutch. The pilot control clutch can decelerate a section of the ball ramp, as a result of which a relative rotational speed is brought about in the ball ramp. As a result, the ball ramp can apply force to the actual clutch pack and generate the locking effect and/or close the clutch.
However, such actuator arrangements with ball ramp and electromagnetically activated pilot control clutch are very large in the axial direction, which makes integration into drive trains difficult.